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Glutamate, released at a majority of excitatory synapses in the central nervous system, depolarizes neurons by acting at specific receptors. Its action is terminated by removal from the synaptic cleft mostly via Na(+)-dependent uptake systems located on both neurons and astrocytes. Here we report that glutamate, in addition to its receptor-mediated actions on neuronal excitability, stimulates glycolysis--i.e., glucose utilization and lactate production--in astrocytes. This metabolic action is mediated by activation of a Na(+)-dependent uptake system and not by interaction with receptors. The mechanism involves the Na+/K(+)-ATPase, which is activated by an increase in the intracellular concentration of Na+ cotransported with glutamate by the electrogenic uptake system. Thus, when glutamate is released from active synapses and taken up by astrocytes, the newly identified signaling pathway described here would …